True, but that's also true of any XML, RSS, Atom, HTML, etc. Websites abuse HTML all the time, and there's nothing saying that just because something is transferred with application/atom+xml that it will be valid or follow the spec.
It's more of a social agreement. If you get a JSON object from a place you expect a JSON Feed and it has a title and items, then it'll probably work, even if it omits other things.
It's more of a social agreement. If you get a JSON object from a place you expect a JSON Feed and it has a title and items, then it'll probably work, even if it omits other things.